AI agents invoke evaluate_smalltalk_with_neo_console to trigger actions in Pharo Nc. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Based on the server description and sibling tools like 'evaluate_code' and 'evaluate_simple', this tool almost certainly evaluates arbitrary Smalltalk code expressions. Executing arbitrary code in a runtime environment is an Execute-category action with critical severity since it can perform any operation including file system access, network calls, or destructive actions depending on the code evaluated.
From the tool's definition Tool name contains 'evaluate_smalltalk' and server description states it 'enables users to evaluate Pharo Smalltalk expressions' via NeoConsole
Attacks that exploit this kind of access
evaluate_smalltalk_with_neo_console. It is categorised as a Execute tool in the Pharo Nc MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Pharo Nc MCP server in PolicyLayer and add a rule for evaluate_smalltalk_with_neo_console: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Pharo Nc. Nothing to install.
evaluate_smalltalk_with_neo_console is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the evaluate_smalltalk_with_neo_console rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for evaluate_smalltalk_with_neo_console. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
evaluate_smalltalk_with_neo_console is provided by the Pharo Nc MCP server (mumez/pharo-nc-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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